We propose to carry out studies in thermal and radiation biology which are a continuation of and a logical progression from work carried out in this laboratory on the effects of hyperthermia on normal and tumor tissues. The focus of the studies will be on the effects of microwave hyperthermia (alone and in conjunction with X-radiation) on critical normal tissues which will be exposed in human patients in clinical trials now under way or under active consideration. The studies include the effects of hyperthermia alone and in combination with X-radiation on normal mouse lung, heart, esophagus, and urinary bladder. Strenuous efforts will be made to evaluate the microwave power to which these organs will be exposed and to carefully control the thermal and radiation dosimetry. Determinations of thermal and radiation damage will employ functional assays and lethality to quantitate damage and establish tolerance levels to the injury. The studies include evaluation of both early and late effects. The experimental design includes both single and fractionated treatment and will allow us to evaluate the effects of fractionation and thermal tolerance. The study avoids single-point assays and evaluates the rate at which normal tissue damage progresses with treatment time and temperature. The establishment of tolerance levels for these normal tissues is preliminary to treatment of appropriate tumors in close association with the normal tissues within established tolerance limits.